If you need new heating and air-conditioning equipment, you want the best price on the highest-quality replacement. If you want to add central air conditioning or extend a system, it is even more important to make the right decisions.

Once you’ve decided on the new heating or cooling system you want to buy, collect bids from high-quality contractors. Each contractor’s proposal should include several elements, all of them important in your choice on the best outfit for your job.

The most important maintenance task for both heating and cooling systems is something you can do yourself—replacing the air filter. Check your filter monthly. When a filter has a matting of dirt—i.e., it’s difficult to see through when you hold it up to a light—it’s time to replace it.

If you are installing new equipment, in addition to making choices about energy efficiency, you will need to decide whether to pay extra for various features. Here is a summary of the types of add-ons.

Since ground-source heat pumps don’t require alternative sources of heat during cold weather, and can more efficiently create warm air from their warmer surroundings, they can be incredibly energy efficient.

Rather than paying for individual maintenance visits and repair jobs, you might consider getting a service contract for air-conditioning and/or heating equipment. Many companies try to persuade customers to enter into such contracts.